Heating, ventilating, and air conditioning (HVAC) systems can be used to regulate the environment within a conditioned space. Typically, an air blower is used to pull air (i.e., return air) from the conditioned space into the HVAC system through ducts and push the air into the conditioned space through additional ducts after conditioning the air (e.g., heating, cooling, or dehumidifying the air). The dehumidifying aspect of an HVAC system may utilize a moisture-altering device or devices.
In a cooling system in which a dehumidifier is desired, the air to be conditioned may be cooled adequately to dehumidify the air and if in a cooling mode can simply provide the resultant airstream to the space to be conditioned. When not in a cool mode, it is necessary to cool the air adequately to dehumidify the air, but then heat it again to a desired temperature range. This may be accomplished using a reheat coil that uses heat from the compressor. To selectively control the flow of the refrigerant to the reheat coil before going to the condenser, a solenoid valve has been used and later other valves, such as a heat-pump valve as shown in FIG. 1.
FIG. 1 presents an HVAC system 100 having a selectively operable reheat device 102 that is coupled to a valve 104 by a pipe 106. The reheat device 102 is also coupled by pipe 108 and pipe 109 to a condenser 110. The pipe 108 may include a one-way valve 112. The condenser 110 is coupled by pipe 114 to an evaporator 116, which has an expansion valve 118 associated with it. The evaporator 116 is coupled by pipe 120 in cooperation with pipe 122 to compressor 124 at a suction portion 125 and by pipe 120 to valve 104. A portion of pipe 120 includes an orifice 126 that is downstream of a guide pipe 128 that is coupled to a guide valve 130. A pipe 132 is coupled to a discharge port 134 of the compressor 124 and to the valve 104. Another guide pipe 136 couples pipe 132 to the guide valve 130. The guide valve 130 is also coupled by guide pipes 138 and 140 to the valve 104, which may be a heat-pump valve. In operation, air is pulled across the evaporator 116 for sufficient cooling to dehumidify the air and then the cooled air is passed by the reheat device 102, which is off if in the cooling mode and is on if in the reheat mode.
While this and other techniques have been used to incorporate reheat features into HVAC systems, improvements in performance and or cost of equipment remain desirable.